The present conventional auto burners are all mechanical actuated, i.e. the flame size is adjusted by changing the rotating direction of the motor of the electric actuator, and by means of a connecting rod that actuates a damper and a fuel oil regulating valve. For example, an autocontrol burner is produced by an German company named Benninghoven (see FIG. 1), which can adjust the flame by changing the rotating direction of the motor of the electric actuator 5 using a rotating direction control circuit 6, and by means of the connecting rod that actuates the damper 4 and the fuel oil regulating valve 3. This kind of conventional auto burner has some defects such as high energy consumption (unable to consider both of the air/oil ratios of light oil and heavy oil at the same time, meanwhile difficult to adjust the air/oil ratio and low precision), low efficiency (the motors of the required blower fan and the oil pump are not only large in power, but also always run at the maximum number of revolutions regardless of the flame size), and complicated mechanical structure, short lifetime, great noise and poor economy environmental index etc.